auto trans thought

[XJSuperman]

This may or may not be my idea and it may not be a good one but I figured I throw it out anyways:



Something for us AUTO trans guys. It may or may not be a good idea BUT I am trying it anyway.

With the 315's I don;t need over drive unless I am doing more than 55 MPH. At 55 or below I run at or below 2000 RPM's... but at or below 35 it is running at around 1400 RPM's or less... plus under 49 MPH (give or take ) the converter doesn;t lock up in 3rd (DRIVE)

BUT... the converter DOES lock up in second gear at around 28-30 MPH... and up to about 38 MPH it is still at or under 2000 RPM's. SO essentially I am attempting to run in 2nd up to 40 MPH. . if I hit over 40 I;ll shift into 3rd. FIgure it may save some heat buildup in the converter PLUS if towing a load under 40 MPH this would be perfect because the converter locks at such a slow speed in 2nd gear.



And don;t flame if this has been discussed... I haven;t seen it.

 

[Gunnernmybike]

Okay, I have a '04 and probably an elementry question but how can you tell when the torque converter locks up?

 

[XJSuperman]

It's easy to feel the trans shift through the gears... put the shifter in 2nd... drive it up easy till it hits second and then get to 28MPH + and you'll feel a second kick... that;s the converter.



Same being in 3rd (drive) when you hit about 50 MPH... you'll feel an extra kick... that again is the converter locking up.

 

[Big Rig]

When you hit 50 mph & the TC kicks in you get a big drop in RPM's, a much bigger drop than when it goes into 4th (OD).

You should be able to feel it, hear it & see it.



Big Rig

 

[XJSuperman]

I have to disagree with the 'bigger' drop ... when the transmission shifts into OD it may drop several hundred RPM's in the engine... the converter locking up may only drop a hundred (if that). When mine locks at 50MPH I'm at about 1800 RPM's and it stays there when the converter locks. If I put it into OD at 50 MPH my RPM's drop to about 1400. Thats much more of a drop than when the converter locks.

 

[geusterman]

xj, I think you brought up a good point about auto's and bigger tires. Even with factory 31's the auto locks up at a pretty low mph which has bothered a few here (Big Bob). Because of the Cummins torque it has not been to big a deal. But when you change ratios and pick up more mph for rpm then the lockup occurs earlier (lower mph). It must be speed regulated and perhaps it is adjustable. I hope so because I want to put my Rickson 19. 5's on. With my 02 6 spd this was not an issue. George

 

[Big Rig]

XJSuperman,



I think the reason you are not seeing the big drop in rpm's when the tc locks up is because you have the "04" 48RE & I have the "04. 5" 48RE. I noticed that you have TC lockup in 2nd gear. I have no TC lockup in 2nd. With my engine at normal operating temp I started in 2nd gear & ran it up to 40 mph. There was only one shift from 1st to 2nd, NO TC lockup. Your rpm's at 38 mph were under 2000 rpm's, my rpm's at 40 mph were 2500 rpm's. Another person (ERK) on another post with an "04. 5" came to the same conclusion that he has no TC lockup in 2nd gear. Hence, the "04" & "04. 5" 48RE transmissions shift differently. My owners manual says not to go up & down steep grades with a heavy load with the trans in 1st or 2nd because of TC slippage which could put an additonal load on the cooling system. Slippage is caused by the TC not being locked up. That indicates to me I have no TC lockup in the low manual gears.

I am telling you all this to say that what you see on TC lockup is not necessarily what I see with an "04. 5" 48re transmission. We are looking at two different things & I can only speak for my "04. 5" Hope this clears things up a little. I wish Dodge would come out with something that told us how exactly these transmissions are supposed to shift. Maybe they haven't made up there minds on how they are supposed to shift... LOL



Big Rig

 

[XJSuperman]

It does clear things up quite a bit. It is pretty bad that for a year and half worth of trucks ('03 thru '04. 5) that there are "technically" 3 different autos.

To my understanding the 1st half of '03 was the 47RE. The '03. 5 was 48RE as was the 1st half of '04... and now the '04. 5 (325/600's) have a different shifting 48RE. Some consistency amongst our trucks sure would be nice if DC could manage!



Of course now some of the manual trans boys will tell us we should quit whining because we should have bought the 6 spd! LOL